The background description provided herein is for the purposes of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Tungsten (W) film deposition using chemical vapor deposition (CVD) techniques is an integral part of semiconductor fabrication processes. For example, tungsten films may be used as low resistivity electrical connections in the form of horizontal interconnects, vias between adjacent metal layers, and contacts between a first metal layer and the devices on a silicon substrate. Tungsten films may also be used in various memory applications, including in formation of buried wordline (bWL) architectures for dynamic random access memory (DRAM), and logic applications. In an example of bWL deposition, a tungsten layer may be deposited on a titanium nitride (TiN) barrier layer to form a TiN/W bilayer by a CVD process using WF6. However, the continued decrease in feature size and film thickness bring various challenges to TiN/W film stacks. These include high resistivity for thinner films and deterioration of TiN barrier properties.